I'm A+ Tech and AppleCare Certified. I work on MacBooks for a living.
I was frustrated with inability to overclock my iPad 2 even while it's jail broken until I found a tip. All Games including Apps run 2x faster after this mod. THIS is not like speed intensifier!

So, let's just get straight to it.
On iOS 7 :
1 Using iFile go to System/Library/CoreServices/powered.bundle/
The file you want is com.apple.SystemPowerProfileDefaults.plist
(Most ppl say rename the file to bak and reboot, WRONG.)
2 Select the file and go to Text Viewer
3 Once in Text Viewer select Edit
4 Change the Integer values of AC / Battery / UPS Power to "2"(Only for the first section of code)
Example:
<key>DefaultProfileChoices</key>
<dict>
<key>AC Power</key>
<integer>2</integer>
<key>Battery Power</key>
<integer>2</integer>
<key>UPS Power</key>
<integer>2</integer>
</dict>

5 Next in the Array:
Change All Dynamic Power Step Integer values to "1"
All GPUSwitch to "3"
All ReduceProcessorSpeed to "0"
Do THIS for all the code until you reach the bottom
6 Save and Respring. Enjoy your new almost iPad Air! Oops I mean IPad 2x!

Quick question: The iPhone 4S runs at 800MHz, but changing these values, does it increase the CPU speed to maybe 1GHz? If I was to increase the CPU speed to lets say 1GHz or 1.5GHz, what would I have to change?

Yes, overclocking should/does drain more power. The reason why they put clocks is to ensure that the battery life is sustainable. Like the gentleman above said, if you do this, you can say goodbye to your long battery life...